It is true that to us humans, the sexual life of many animals seems strange. However, a closer look reveals that the animal with the most bizarre sexual behavior is actually the human.

We are the only social species that insists on having sex privately, not in public view. We have sex at any moment, even if the female is unable to conceive (for instance, when she is pregnant, during her fertile cycles, or after menopause). A woman is unaware of the exact timing of her fertility and does not communicate it to men by emitting scents or cries or even changing colors in areas of her body.

Why do we differ so radically from our closest relatives, the anthropoid apes? Why does menopause occur only in women among all mammals? Why are humans among the few mammals where the male often or usually stays with the female for child-rearing? And why is the male penis so unnecessarily large?

The answers to all the questions regarding how evolutionary forces acted on our distant ancestors to differentiate us so much from them can be found in this book by one of the most renowned experts in the fields of physiology and evolutionary biology.